A determined person could easily gather such photos to create a database of your friend's faces, then use facial recognition software to identify the social authentication photos. (newscientist.com)
These concerns will be amplified with the «internet of things» that will track our physical objects and the increasing use of facial recognition software. (blog.politics.ox.ac.uk)
Allowing owners to match their pets with facial recognition software, the app will scan your pet's facial features and match against pets found. (k9magazine.com)